This study explored the contribution of finger counting habits to the association of numbers with space (the SNARC effect). First, a questionnaire study indicated that two-thirds of 445 adults started counting on their left hand, regardless of their handedness. Secondly, a group of 53 "left-starters" but not a group of 47 "right-starters" showed a SNARC effect in a parity task. A significant difference in the strength of the effect between groups suggests that finger counting habits indeed contribute to the association between numbers and space in adults. (c) 2007 Elsevier Masson Srl. All rights reserved.